A process and device for nitrogen-enriched bog liquefaction

Abstract

A nitrogen-enriched BOG liquefaction process and device. The process includes: the reheated low-temperature BOG is increased to high pressure by a compressor, pre-cooled and throttled, and most of the BOG is liquefied and nitrogen is removed by using the principle of high-pressure throttling refrigeration, and the nitrogen content of the obtained product LNG is less than 1%. The BOG liquefaction process provided by the process of the invention is simple, the refrigerant is single, and has little impact on the original system, and is especially suitable for the transformation of LNG storage and distribution stations, and can adapt to the nitrogen content of about 2% to 20% in the BOG.

Description

technical field [0001] The invention provides a nitrogen-enriched BOG (Boil Off Gas) liquefaction process and device, which is suitable for reliquefaction of BOG produced by LNG storage tanks and LNG loading and unloading systems. Background technique [0002] At present, my country's LNG industry is still in the development period, and BOG release is a relatively common phenomenon. For some LNG facilities with insufficient supporting vehicles and users, the annual release volume can often account for more than 10% of the total purchased gas volume. Serious It can even reach 30%. Reliquefaction of BOG can effectively alleviate the problem of frequent release of BOG in LNG filling stations and other LNG facilities. With a design gas filling capacity of 10000Nm 3 / d LNG filling station as an example, if the release rate is 10%, the annual direct economic loss is close to 200,000 yuan. It is extremely economical to reliquefy BOG to avoid this part of the cost loss as much as ...

AI Technical Summary

Problems solved by technology

The release of BOG not only wastes energy, but also brings the risk of combustible gas combustion and explosion. At the same time, it causes serious greenhouse effect and pollutes the environment, which runs counter to my country's planning goals of environmental protection, energy conservation and emission reduction, and sustainable development.

[0004] At present, the liquefaction of BOG is mostly applied in that BOG enters the cold box after being pressurized by the compressor, and is liquefied under the cooling action of the refrigerant in the cold box. This process has a certain dependence on the original natural gas liquefaction system, especially BOG When the amount of BOG fluctuates greatly, it is easy to affect the stability of the natural gas-refrigerant heat exchange system in the cold box, and it is necessary to add a special BOG heat exchange flow channel, so the structure of the cold box is more complicated

At the same time, if the nitrogen content is high, a rectification tower must be used, and the process and operation are complicated

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